Json Values Append Array but ViewDidLoad it seem Empty [Swift]

I am working in iOS and when I take JSON datas , I print it with no error in the function and append it a String array ( i did it correctly )

But if i want to reach to String array later the json Function it seem empty array . For testing I printed the array in a Button Action then it worked for me but i want to use in String Datas in other Function when Json Function ends .